Ethical Hacking News
A recent discovery by a cybersecurity firm, V12, has revealed a critical vulnerability in the x402 SDKs, which can be exploited by malicious APIs to drain the token balances of AI agents. Developers are advised to update their applications to the latest releases of the x402 SDKs to mitigate the risk.
V12 discovered a critical vulnerability in the x402 SDKs that can be exploited by malicious APIs to drain the token balances of AI agents. The vulnerability lies in the default client of the x402 SDKs, which sets no spending limit until a recent release on August 18 added one. There are 25 total flaws in the x402 code, with three of them rated critical and described in detail. The x402 Foundation has not published a security advisory for the three critical flaws, despite having fixed them in the August 18 releases. Developers are advised to update their applications to the latest releases of the x402 SDKs to mitigate the risk. Setting spending limits can prevent malicious APIs from draining the token balances of AI agents.
A recent discovery by a cybersecurity firm, V12, has shed light on a critical vulnerability in the x402 SDKs, which can be exploited by malicious APIs to drain the token balances of AI agents. The x402 SDKs, developed by the Linux Foundation, are an open standard that allows software, including AI agents, to pay for API calls within the web request itself, without requiring a person to approve each payment.
The critical flaw, which was discovered by V12, lies in the default client of the x402 SDKs, which sets no spending limit until a recent release on August 18 added one. The risk was limited to agents who automatically signed payments and whose apps set no limits. This means that a malicious API could use the x402 SDKs to sign a payment for the full balance of a supported token, which could then be used to collect the funds.
V12's researchers found 25 flaws in the x402 code, with three of them rated critical and described in detail. The foundation that maintains the SDKs, had already fixed all three critical flaws in the August 18 releases. However, the foundation has not published a security advisory for the three flaws, and its changelogs list the fixes without calling them security fixes.
The x402 SDKs are widely used by developers, including those who work on AI and blockchain-related projects. The recent discovery highlights the importance of keeping software up to date and regularly reviewing the code for security vulnerabilities.
In addition to the critical flaw, V12 also found two other vulnerabilities in the x402 SDKs, one of which allowed a facilitator to accept a Solana transaction that moved no tokens as a valid payment. This could be used by a malicious server to deliver a paid resource while receiving no tokens. The other vulnerability allowed a malicious server to get an agent to sign a login message for a different website.
The x402 Foundation has published updates to the SDKs, including new releases for TypeScript, Python, and Go. These updates include spending limits, which can be set by developers to prevent malicious APIs from draining the token balances of AI agents.
To mitigate the risk, developers are advised to update their applications to the latest releases of the x402 SDKs, which include the fixes for the critical flaw and other vulnerabilities. Developers who cannot upgrade yet can register a payment policy that drops any option above a set amount. The older clients support this with register_policy in TypeScript and Go, and register_policy in Python.
The discovery of the critical flaw in the x402 SDKs highlights the importance of keeping software up to date and regularly reviewing the code for security vulnerabilities. It also underscores the need for developers to be aware of the risks associated with using open standards like x402 SDKs and to take steps to protect their applications and data from malicious attacks.
A recent discovery by a cybersecurity firm, V12, has revealed a critical vulnerability in the x402 SDKs, which can be exploited by malicious APIs to drain the token balances of AI agents. Developers are advised to update their applications to the latest releases of the x402 SDKs to mitigate the risk.
Related Information:
https://www.ethicalhackingnews.com/articles/Critical-Flaw-in-x402-SDKs-Exposes-AI-Agents-to-Malicious-API-Attacks-ehn.shtml
https://thehackernews.com/2026/10/critical-x402-sdk-flaw-could-let.html
https://imtr.net/article/critical-x402-sdk-flaw-could-let-malicious-apis-drain-ai-agents-token-balances-ef05
Published: Fri Oct 23 05:05:55 2026 by llama3.2 3B Q4_K_M
